The present invention relates to an active magnetic bearing with radial magnetic flux for a rotary machine presenting an axis of rotation OO′, the magnetic bearing comprising a stator fitted with electromagnet windings and with a first stack of ferromagnetic laminations extending essentially perpendicularly to the axis OO′, a rotor fitted with a second stack of ferromagnetic laminations extending essentially perpendicularly to the axis of rotation OO′, servo-control circuits for maintaining the rotor in equilibrium without contact with the stator, and at least one detector for detecting the radial position of the rotor and at least one detector for detecting the axial position of the rotor, which radial and axial position detectors deliver signals to said servo-control circuits, and the currents carried by the electromagnets of the stator are servo-controlled on the basis of said signals.
Most applications which use magnetic bearings conform to the concept shown in FIG. 8. That concept corresponds to clear separation between the various components, and in particular between a radial magnetic bearing 200, a radial position detector 201, and an axial position detector 301.
In some cases, as described for example in document FR 2 632 451, the device has first and second radial detectors disposed respectively in the vicinity of a radial magnetic bearing and of a conical magnetic bearing, and extending around the rotor over an angular sector of 180°. Such a device further comprises an axial detector extending around the rotor over an angular sector of not more than 180° and disposed in the vicinity of the conical magnetic bearing substantially in the same radial plane as the second radial detector. Thus, the axial and radial detectors are combined, and use the same ring of rotor laminations. Nevertheless, those detectors are not integrated in a bearing.
In other cases, such as described for example in patent FR 2 094 326, the radial detectors are interposed between radial bearings, but axial detection remains independent.
In each of those cases, the juxtaposition of bearing stacks, radial detectors, and axial detectors leads to a system in which the length of the bearing function as a whole is large and in which the dynamic behavior of the rotor leads to problems.
In addition, as can be seen in FIG. 9, having a difference in position, i.e. non-coincidence between the radial detection point 202 and the reaction point 203 of the radial bearing makes servo-control considerably more complicated to define. Deformation due to the mechanical design of the rotor can cause nodes 204 to be situated between the radial bearing 200 and the radial detector 202, in such a manner that phase reversals occur between detection and reaction, which leads to erroneous reactions by the magnetic bearing.